“Where did you read all that?” inquired Eph, looking both astonished and sheepish.

“Here,” replied Jack, going to a small wall book-case, taking down a book and turning several pages before he stopped.

“Just my luck,” muttered Eph, disconsolately.  “Here I’ve been dull as ditch-water for an hour, trying to find out something new, and it’s all stated in a book printed—­ten years ago,” he finished, after rapidly consulting the title-page.

Jacob Farnum had been no listener to this conversation.  Taking the marine glasses from the conning tower, the shipbuilder was now well forward on the platform deck, scanning what was visible of the steam craft to the southward.  At last the yard’s owner turned around to say: 

“I don’t believe you young men can have things ship-shape a second too soon.  The craft heading this way has a military mast forward.  She must be the ‘Hudson.’  If there’s anything to be done, hustle!”

Jack and Hal sprang below, to scan their respective departments.  Five minutes later Grant Andrews hailed from the “Pollard,” and Eph rowed over in the shore boat to ferry over the machinists.

Half an hour later Andrews and his men had put in the few needed touches aboard the newer submarine boat.  The sun, meanwhile, had gone down, showing the hull of a naval vessel some four miles off the harbor.

Darkness came on quickly, with a clouded sky.  As young Benson stepped on deck Grant Andrews followed him.

“All finished here, Grant?” queried the yard’s owner.

“Yes, sir.  There’s mighty little chance to do anything where Hal Hastings has charge of the machinery.”

“That’s our gunboat out there, I think,” went on Mr. Farnum, pointing to where a white masthead light and a red port light were visible, about a mile away.

“Dunhaven must be on the map, all right, if a strange navigating officer knows how to come so straight to the place,” laughed Jack Benson.

“Oh, you trust a United States naval officer to find any place he has sailing orders for,” returned Jacob Farnum.  “I wonder if he’ll attempt to come into this harbor!”

“There’s safe anchorage, if he wants to do so,” replied Captain Jack.

While Somers was busy putting the foreman and the machinists ashore, Mr. Farnum, Jack and Hal remained on the platform deck, watching the approach of the naval vessel, which was now plainly making for Dunhaven.

Suddenly, a broad beam of glaring white light shot over the water, resting across the deck of the “Farnum.”

“I guess that fellow knows what he wants to know, now,” muttered Benson, blinking alter the strong glare had passed.

“There, he has picked up the ‘Pollard,’ too,” announced Hastings.  “Now, that commander must feel sure he has sighted the right place.”

“There go the signal lights,” cried Captain Jack, suddenly.  “Hal, hustle below and turn on the electric current for the signaling apparatus.”